"More than half of people in the UK are overweight and one in four is clinically obese. And the fact of the matter is it is very hard to lose weight once it is there, so if we could help people before they get to that stage then that is obviously beneficial."

In the UK more than one third of men and women will be clinically obese by 2030, costing the NHS an extra £19.2bn (€24bn) a year.

Tam Fry of the National Obesity Foundation said the drugs could help overweight people but advised against giving them to young people before they gained weight.

"We're heading in the right direction and drugs like this could be the Holy Grail in fighting the obesity epidemic," he said.

"But the problem with the middle-aged spread is that it is caused by a number of factors. if you exercise and eat healthily then a lot of these problems will go away."